Interventions for Reducing Ambient Air Pollution and Their Effects on Health: Final Results from a Cochrane Systematic Review

摘要

Interest in assessing the health effects of air quality interventions has grown in response to questions about the benefit of further tightening air pollution regulations. No systematic review has been performed to date with transparent and standardized protocols. In brief, standardized protocols were followed for study selection, assessing individual study quality and evaluating the body of evidence. Eligible studies assessed the effectiveness of any intervention aiming to reduce ambient PM air pollution from vehicular, industrial, residential or multiple sources with a range of study designs. Primary outcomes were PM concentrations and all-cause as well as cardiovascular and respiratory mortality. After a three-stage duplicate screening process of 33.462 unique titles, we included 44 interventions evaluated in 53 studies in 20 countries in the main analysis. Changes in PM10 and PM2.5 were assessed for 22 and 11 interventions, respectively, while only 16 studies assessed changes in health outcomes, including 9, 4 and 5 studies assessing total, cardiovascular and respiratory mortality, respectively. Studies included in the main analysis comprised controlled-before after studies and interrupted time series studies with and without a control site. Study quality varied widely. A graphical summary of the evidence showed that effect estimates were heterogeneous, and only some studies documented improvements in air quality and/or health. Given the few studies and the heterogeneity across interventions, outcomes, and study methods, it was difficult to generate any overall conclusions regarding the effectiveness of interventions in improving air quality or health. The review highlights the numerous challenges encountered such as lack of statistical power, background trends, and difficulties in direct attribution. The review provides possible directions and implications for future practice and research, including the use of causal inference methods that has shown promise.